So while I've been enjoying using extension tubes and a lens coupler, I am starting to get more serious about getting an actual macro lens. And while I am not planning on getting one for several more months, I will probably get one this year and push getting a new camera body into next year.

So that said, I am curious as to which macro people would prefer/recommend. My signature is up to date for what lenses I have acquired thus far, if that affects anyone's recommendation. I am already leaning in one direction and this poll may or may not affect my thoughts.

If you have an experience with one, or more, of these and wish to share, then do so. If you have a radical lens recommendation that you think I might not have considered, then please share it and why.

While I have been going through lenses and trying some out in the store, I am still roughly in the gathering data stage. Two of the lenses were not even in my consideration two months ago. One of which I was unaware of until recently.

That said, here are the main contenders:
All of these options have 1:1 macro capability and take really good photos from what I see. So I am currently doubting I would see much image quality difference between them in a real world application. Feel free to disagree if you have some experience with at least two of the following.

1) Canon EF-S 60mm f/2.8 USM Macro.
Positives:
Least expensive option. This is not insignificant.
Compact lens. This means it will be very easy to justify having it with me as I do with my 50mm f/1.4 USM lens.

Neutral:
While this does not take the same size filters as any of my other lenses, 52mm filters are relatively inexpensive and compared with the money I would save on this lens, this is not really a factor.

Negatives:
Will not upgrade to a full frame camera in the future.
60mm is already covered, or close to being covered, by other lenses that I have. Including primes.
Least working distance.

2) Canon EF 100mm f/2.8 USM Maco. (Non-L)
Positives:
Takes 58mm filter, which is similar to several lenses that I own.
Would work with my coupler that I've enjoyed on other lenses. This means I would have options for expanded macro capability if I so desired.
Would work on a full frame camera.

Neutral:
Not the least expensive, but not the most either.
Medium working distance.

Negatives:
Besides 2 zooms that cover this range, I also have the 85mm f/1.8 USM prime that is very close in focal length. I don't foresee a situation where I would want both lenses with me.

3) Sigma 150mm f/2.8 AF APO EX DG OS HSM Macro.
Positives:
Longest working distance of the three.
The only lens in this range that I have is my 70-300mm f/4-5.6 DO IS USM. Even if I have both with me, they would complement each other rather than supplement.
Full Frame compatible.
Comes with a tripod collar.
OS: Optical Stabilization. While this is not the IS system that Canon uses, it is the only one of these three I'm looking at that has it.

Negatives:
Most expensive. (Not insignificant)
Heaviest.
Will not take the same filters as my other lenses, though I could get a step-down adapter to convert some of my 77mm filters if needed.
Not compatible with my coupler if I wanted to try it in the future.

Really Minor Annoyance, but stating it anyway.
All the acronyms. The way I do my signature here means that I would use all of them and that is just a tad bit annoying. On the one hand I want to be accurate, on the other, I do not particularly care for it and will probably just shorten it.

I do not own any of these three, but do have a few thoughts, with the disclaimer that I do not regard myself as any kind of authority on macro lenses, though I find macro very important as one part of my crime scene photography. With a good macro/telephoto lens, I may be able to shoot a whole scene without changing lenses.

First, I do not use filters on macro lenses, so the uncommon filter sizes of my Canon 100mm Macro 2.8L and our Tokina 100mm 2.8 are non-issues.

Second, be sure to consider your working distance for 1:1 in relation to your subject. Living things may not tolerate a lens being too close to them. The listed distance in specifications, unless otherwise stated, is usually from subject to sensor.

I do remember that one of my local instructors compared a Sigma macro lens with a Canon macro lens, at the dealer, and found the individual Canon to have more distortion than the individual Sigma, so he purchased the Sigma. Keep in mind this could be sample variation, and does not mean all Sigmas have less distortion than all Canons! The lesson here is to try the individual lenses, if feasible, before purchase.

Consider whether you want your macro lens to serve double duty, as a telephoto. That is why I bought my 100L, because I wanted a fairly fast weather/dust-resistant lens with Image Stabilization in the 100mm range, with a night-time aerial surveillance assignment speeding my decision to buy when I did. (A 70-200mm 2.8 with IS was beyond my budget at the time.) The beautiful bokeh of the 100L adds to its usefulness!

While on the subject of bokeh, try taking a look at the Tokina 100mm, which has nice bokeh. I like the push-pull AF-MF clutch, though now that I have my 100L, the Tokina sees little use.

I'd add option 2.5 for consideration: The Sigma 150mm non-OS model, which has slightly longer working distance than the OS model not to mention being cheaper too. You do get the added complication if it is worth the extra for OS, there are more used non-OS models out there which can help the budget too.

Overall, I find a longer working distance easier to work with most of the time, but like any other photography, the field of view does come into play so a 150mm macro shot would look different than a 60mm macro shot of the same sized subject. While I like the extra background separation a longer focal length gives, sometimes I also wish for something wider to give the subject a bit more context.

My overall answer would be you can't go really wrong with any of these macro lenses. I wouldn't worry about their optical performance, leaving you to decide on other factors.

A lens coupler is a double sided filter. So you attach the front end of two different lenses to each other allowing for greater magnification. So far, my favorite combination is to use my 70-300mm DO with my 85mm prime attached to it.

The 150mm non-OS sigma is also something that I've considered at times. The reason I listed the OS version was due to wanting to hand hold macro at times and I thought the OS version would be better for that. The difference for a new one here is $200.

The new thread is a lot broader question than this one, and I'm hoping it will be better. In light of this, I'm going to ask that this thread be locked. Though I am not seeing an option to do that here.